Speckle-based paper authentication employs a roughness pattern for individual pieces of paper and their corresponding speckle as an identifying signature. The paper is permanently fixed to an elaborate mechanical plate that fits in a magnetic mount, to ensure accurate viewpoint reproduction. The object of interest can also be moved and placed against a scanner.
Speckle interferometry can measure out-of-plane deformation (i.e., along the camera optical axis), but current methods require a reference laser under highly calibrated settings, for example, using a beam splitter.
Speckle patterns can enable the use of traditional computer vision techniques to track objects such as white walls, transparent surfaces, or fluids that would otherwise be featureless. For very small translations parallel to the image plane, the specific patron is simply translated. The applications include in-plane deformation measurement, flow visualization, and motion sensing. Since laser speckle depends on the geometry at the scale of the laser wavelength (e.g., 1 μm), geometry can be inferred from the observed pattern.
Skin contact usually leaves traces of body fluids on a surface that can be detected using fluorescent fingerprint powder and UV light, or other chemical methods, which is limited to bare-skin contact with non-porous surfaces.